restructure render loop to correct timings and expose FFI methods for setBoneTransform/setMorphWeights

lib/filament_controller.dart

@@ -485,4 +485,11 @@ abstract class FilamentController {
       double orbitSpeedX = 0.01,
       double orbitSpeedY = 0.01,
       double zoomSpeed = 0.01});
+
+  ///
+  /// Finds the child entity named [childName] associated with the given parent.
+  /// Usually, [parent] will be the return value from [loadGlb]/[loadGltf] and [childName] will be the name of a node/mesh.
+  ///
+  Future<FilamentEntity> getChildEntity(
+      FilamentEntity parent, String childName);
 }

lib/filament_controller_ffi.dart

@@ -125,7 +125,9 @@ class FilamentControllerFFI extends FilamentController {
 
   @override
   Future setFrameRate(int framerate) async {
-    set_frame_interval_ffi(1.0 / framerate);
+    final interval = 1000.0 / framerate;
+    set_frame_interval_ffi(interval);
+    dev.log("Set frame interval to $interval");
   }
 
   @override
@@ -596,7 +598,7 @@ class FilamentControllerFFI extends FilamentController {
       weightsPtr.elementAt(i).value = weights[i];
     }
     var meshNamePtr = meshName.toNativeUtf8(allocator: calloc).cast<Char>();
-    set_morph_target_weights(
+    set_morph_target_weights_ffi(
         _assetManager!, entity, meshNamePtr, weightsPtr, weights.length);
     calloc.free(weightsPtr);
     calloc.free(meshNamePtr);
@@ -1178,7 +1180,7 @@ class FilamentControllerFFI extends FilamentController {
     var meshNamePtr = meshName.toNativeUtf8(allocator: calloc).cast<Char>();
     var boneNamePtr = boneName.toNativeUtf8(allocator: calloc).cast<Char>();
 
-    var result = set_bone_transform(
+    var result = set_bone_transform_ffi(
         _assetManager!, entity, meshNamePtr, ptr, boneNamePtr);
 
     calloc.free(ptr);
@@ -1188,4 +1190,21 @@ class FilamentControllerFFI extends FilamentController {
       throw Exception("Failed to set bone transform. See logs for details");
     }
   }
+
+  @override
+  Future<FilamentEntity> getChildEntity(
+      FilamentEntity parent, String childName) async {
+    var childNamePtr = childName.toNativeUtf8(allocator: calloc).cast<Char>();
+    try {
+      var childEntity =
+          find_child_entity_by_name(_assetManager!, parent, childNamePtr);
+      if (childEntity == _FILAMENT_ASSET_ERROR) {
+        throw Exception(
+            "Could not find child ${childName} under the specified entity");
+      }
+      return childEntity;
+    } finally {
+      calloc.free(childNamePtr);
+    }
+  }
 }

lib/generated_bindings.dart

@@ -736,6 +736,16 @@ external ffi.Pointer<ffi.Char> get_name_for_entity(
   int entityId,
 );
 
+@ffi.Native<
+        EntityId Function(
+            ffi.Pointer<ffi.Void>, EntityId, ffi.Pointer<ffi.Char>)>(
+    symbol: 'find_child_entity_by_name', assetId: 'flutter_filament_plugin')
+external int find_child_entity_by_name(
+  ffi.Pointer<ffi.Void> assetManager,
+  int parent,
+  ffi.Pointer<ffi.Char> name,
+);
+
 @ffi.Native<ffi.Void Function()>(
     symbol: 'ios_dummy', assetId: 'flutter_filament_plugin')
 external void ios_dummy();
@@ -1092,6 +1102,34 @@ external int get_morph_target_name_count_ffi(
   ffi.Pointer<ffi.Char> meshName,
 );
 
+@ffi.Native<
+        ffi.Void Function(ffi.Pointer<ffi.Void>, EntityId,
+            ffi.Pointer<ffi.Char>, ffi.Pointer<ffi.Float>, ffi.Int)>(
+    symbol: 'set_morph_target_weights_ffi', assetId: 'flutter_filament_plugin')
+external void set_morph_target_weights_ffi(
+  ffi.Pointer<ffi.Void> assetManager,
+  int asset,
+  ffi.Pointer<ffi.Char> entityName,
+  ffi.Pointer<ffi.Float> morphData,
+  int numWeights,
+);
+
+@ffi.Native<
+        ffi.Bool Function(
+            ffi.Pointer<ffi.Void>,
+            EntityId,
+            ffi.Pointer<ffi.Char>,
+            ffi.Pointer<ffi.Float>,
+            ffi.Pointer<ffi.Char>)>(
+    symbol: 'set_bone_transform_ffi', assetId: 'flutter_filament_plugin')
+external bool set_bone_transform_ffi(
+  ffi.Pointer<ffi.Void> assetManager,
+  int asset,
+  ffi.Pointer<ffi.Char> entityName,
+  ffi.Pointer<ffi.Float> transform,
+  ffi.Pointer<ffi.Char> boneName,
+);
+
 @ffi.Native<ffi.Void Function(ffi.Pointer<ffi.Void>, ffi.Bool)>(
     symbol: 'set_post_processing_ffi', assetId: 'flutter_filament_plugin')
 external void set_post_processing_ffi(